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All,
I need some info on how the pink with black stripe wire runs from the power window relay back to the fuse box. Does it make any stops along the way? Does it plug into the front of the fuse panel or come in from behind the fuse panel?
The wiring diagram for the defogger switch and the wiring diagram for the power window relay both show a pink / blk stripe wire going to the "ign" port on the fuse panel next to the instr fuse on the fuse panel, but I don't see a connection like that. I have no power on the pink / blk stripe wires at the PW relay and the defogger switch, so I think I have a problem between those connections and the fuse box. Can someone with a wiring harness out tell me where those wires run? Do they run to the gauges next, or run all the way back to the fuse panel? Where do the pink/blk stripe wires from defogger switch and PW relay come back together? I have the individual wiring diagram of the defogger switch and PW already, but I cannot find where the pink / blk stripe wire is near the fuse panel.
Here is the background:
I was trying to diagnose why the defogger was not working on my 1978 Corvette with a test light. At the defogger switch, I had power to the Pink/blk wire when the ignition was turned on but no power to the Lt Blu wire. While poking the test light I actually crossed a couple tabs at the defogger switch and there was a tiny spark. After that spark I could get no power reading at the Pink/blk wire. I gave up on my diagnosis and put the driver's side console access panel back on. When I went to move the car I discovered the power windows don't work, the tach no longer goes below 3500 and the amp gauge does not work. I can do without the window fogger, but not everything else.
I tested the "gauges" fuse and it is good. Hot on both sides. The Pink/black wire at the PW relay was also dead, which is not surprising because both get power from the same source. I jumped a hot wire to the Pink/blk wire connection at the defogger switch and was able to put the windows back up. So I know the problem is upstream of both the defogger switch and PW relay. At the fuse box it is apparent that not every wire is virgin, but not too bad. On the ignition connection, next to the gauges fuse on the fuse box is a plug that looks unique to fit into that connection and a pink wire runs from that to the brake light switch. That wire is hot when the ignition is on. At the brake light switch is a red wire that connects at the same location. It was hot when the brakes are not on and it was dangling down, unprotected or covered....something I don't like to see.
Near the fuse panel, I did discover a Pink/blk wire that was not connected to anything with a stripped area all aged. Maybe at one time someone had stuck that into one of the fuse tabs, as the length was about right. The Pink/blk dangling wire had was not hot, with or without the ignition switch. Using an ohm meter, I tried to see if the dangling wire end had continuity to the Pink/black wire at the defogger switch, but could not get a reading. Verified the ohm meter was working by demonstrating connectivity between the pink/blk wire at the defogger switch and the pink/blk wire at the window relay.
Feeling desperate, I connected power to the dangling pink/blk wire, but got no power to the pink/blk wire at the defogger switch.
Short of tearing out the dash to trace the pink/blk wire from the console, does anyone have any ideas?
As you can see from the picture of my fuse panel, there is a pink wire (no stripe) that plugs in next to the gauges fuse (just to the left). In the PW wiring diagram, it implies more than one wire goes in there ... but not on mine. The solid pink wire runs to the brake light switch.
Meanwhile there is a pink / black stripe wire in the background that is part of a 4-wire plug into a black box labeled phillips. I don't know what that box does.
Like a nightmare you can see a pink / w black stripe wire dangling out the top of the picture. The stripped part of the wire continues thru most of the picture. It is not hot, nor does it show continuity to the pink / blk stripe wire at the PW switch. I did put power to that wire, but it seemed like it had no effect.
By the picturs you posted you harnass maybe different than mine. I did trace the pink wire from the defrost circuit to a red connector, that has a match on a pink and black wire that splits off a few times but comes from the ignition pin on the fuse block in the third pic. Hope this helps
According to the factory Corvette electrical troubleshooting manual for the year in question, you pics appear to indicate a late production 78 w/o rear window defogger. Thus, the Pnk/Blk wire from the power window relay (as well as that from the interior light delay timer, if applicable) should enter directly into the block via the IP Harness Connector. The sole Pnk wire you see at the IGN plug goes to the cruise control release switch.
FWIW, 79's were the first model year to get the ATO blade fuse block, so that year may not be an accurate cross-reference.
Kacyc3, might that fuse block be available?
Last edited by TheSkunkWorks; 10-21-2014 at 10:14 PM.
Because the tach is stuck now at 3500, I pulled up the wiring diagram on the gauges. They are all fed by a pink with blk stripe wire that goes to the gauges fuse. Not only the tach and other gauges are supplied buy the pink/blk but also the brake warning light.
Sure enough the brake warning light no longer works. It does very faintly light up in the darkness. And the oil pressure gauge jumps when the hand brake is pulled on and off. The tach will move from 3500 upwards when I really rev the engine, otherwise is stuck on 3500.
Thanks for the info. This Corvette has seen a lot of use, so there may be significant changes over time. But the build date is March and the rear window and console have the window defogger setup. It has the cruise control too.
Looks like there was some melting going on at one point that affected the brake light switch two wires and the pink/blk stripe wire that hangs down in the center of the pic. Maybe someone replaced the wire from the fuse box to the cruise release with a non-defogger setup? Someone stripped that wire and it looked like someone had spliced the loosely hanging pink / blk in at one time.
What would cause the brake warning light to only faintly work?
March would be late production for 78, as I believe they were cutting off orders in April or May.
Another of those Pnk/Blk wires coming from the 10 amp GAUGES fuse is a 14 g one which subsequently branches off via an 18 g to the IP gauge pack printed circuit, an 18 g to the tachometer, a 20 g to the brake warning light, and an 18 g to the seatbelt/headlight/ignition key warning module (which appears to be missing from the connector hanging loose to the right of your block). FWIW, there's also a 14 g Pnk/Blk wire that serves the turn signal and backup light circuit, but that one should run from the 20 amp DIR SIG BK UP fuse.
Possible causes of a faint brake warning light may include a faulty/poorly grounded park brake warning switch, brake pressure switch or ignition start switch, or a weak ground short somewhere among the Tan/Wht wires otherwise associated with that side of the brake warning light circuit.
If your rear defogger works, it has apparently been rewired elsewhere other than to the IGN plug via the 20 g Pnk/Blk wire as shown in the book.
I do hope that helps, but from this point on the best advice I can likely offer would be to find a copy of the book I'm referencing (below), or another full-color wiring diagram specific to the 78.
Last edited by TheSkunkWorks; 10-21-2014 at 11:42 PM.
If you have the time and confidence I highly recommend you rewire the entire car. I believe the rear defroster being used over time is what almost set my car on fire.
DUB,
I have several parts to wiring diagrams from searches on the forum. I do have a volt/ohm meter....I am in SC about 2 hrs from Charlotte. Thanks for the offer, I sent you a PM.
10-20-2014, 11:04 PM
Anyone have the 1978 dash wiring harness out?
Keith
